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Topics - AmbientChaos

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Questions / Spinning weapon design
« on: February 03, 2017, 08:07:41 am »
I'm in the process of trying to design a spinning weapon for a 3lb bot.  Assuming that the bot will have a top speed of about 5-6 mph and a weapon speed of about 10,000 rpm, how much "bite" should I be shooting for in a single-tooth design?  I have come up with an easy to machine design where the tooth is about 0.25" longer than counterweight end of the weapon, but I need to figure out if that is enough or if I should adjust the design for more bite.

Questions / Bending titanium
« on: October 26, 2016, 10:20:55 pm »
I'm thinking about making a titanium wedge for a bot, something vaguely like what is in the D2 kits, and I'm just trying to figure out the best way to do it. (I've learned my lesson and I'm trying to plan ahead instead of buying a slab of metal and trying to figure out how to form it after the fact.) What would be the best way to make the bends for the sides of a wedge? Using a small hydraulic press? A bending brake?

I've heard of others trying this by taking a torch to the metal and hammering it in a vise with mixed results.  Instead of trying to do something like that with basic tools to get an "okay" result, I'd be happy to make a small investment in an appropriate tool if I could use it multiple times and it would give me a better result. (I'm slowly building up a small bot-building workshop in my basement one tool at a time.)

Questions / Comparing brushless motors
« on: October 16, 2016, 11:30:33 pm »
I'm considering changing out the brushless motor that I am using to drive my weapon, but I would like some confirmation on my guesswork as to how I've been trying to compare the motors.  If I was comparing two brushless motors that had the same Kv rating but a different rating for Power (w), would the one with the higher power rating have more torque and be able to get the weapon up to speed faster?   Also, what is a good speed for antweight weapons to get the best bite, 5,000 rpm?  Or is it more a matter of the tip speed of the weapon than the rpm?

General Robotics Discussion / Off-the-shelf insect weight blades
« on: October 16, 2016, 01:08:23 am »
Since I don't have an enormous amount of CAD experience and I don't have a lot of tools to machine precision parts for a weapon, I have mostly focused on off-the-shelf options for weapon blades.  When it came to looking for off-the-shelf options for insect weight weapon blades I had been able to find a decent range of edger blades that would serve for a beetleweight weapon, but when it came to looking for blades for an antweight all I could find for the longest time were the chipper blades from FingerTech.  I recently discovered that the chipper blades from FingerTech are the type of blades that are found in dado blade sets for table saws, which now gives a new range of options for antweight blades that I hadn't seen before.  I just got a dado blade set that came with two chipper blades that are about 50g heavier and one that is 10g lighter than the FingerTech blades.  I just thought that since I didn't know about this type of blades before now, there could be a number of others that didn't know either, so I thought I would share my discovery here.

Questions / Receiver power supply
« on: October 15, 2016, 02:57:30 pm »
I am thinking that at least some part of the issues I had at Franklin Institute were due to receiver issues, but it remains to be seen if they were reception issues or power issues.  I had OrangeRX 615 receivers and I am considering buying replacement Spektrum receivers to try and cover the reception side of things, but I remember reading somewhere that having multiple ESCs with BECs could wind up causing issues as well. 

In both of my bots I have two TinyESCs providing BEC power to the receiver.  Could this cause reception issues?  Should I disable the BEC on one of the ESCs?

Questions / Milling with a drill press
« on: October 10, 2016, 01:55:11 pm »
I know that using a drill press to mill metal wouldn't be a good idea.  What I want to know is if it would be okay to mill plastic like UHMW with an end mill in the chuck of a drill press?  I don't want to fork out for a small mill just yet, but I just was wondering where the line was for what I could safely do without damaging the drill press.  Is this possible, or should I just stick to drilling?

Questions / Durability of 3D printed parts
« on: August 13, 2016, 09:00:48 am »
I'm planning on getting a 3D printer again before the end of the year, and I've been thinking about what I could and couldn't use it for with antweight/beetleweight robots.  I have some ideas about printing some chassis that would be fun but really hard for me to build otherwise (like Stance Stance Revolution), but I recognize that this won't result in the most durable chassis, it would be mostly about the fun.

My question to the more experienced builders is this: What (non armor/chassis) parts for a bot could I 3D print and expect to have it hold up for a match or three?  My first thoughts were that combined with some heat-set inserts I might be able to make some drive motor mounts or custom weapon motor pulleys that might be able to survive most matches because they wouldn't be under as much direct stress.  Do you think this could work?  What other parts might this work for?

Questions / Mounting electronics
« on: April 09, 2016, 08:25:19 pm »
After my first attempt at wiring up my beetleweight I didn't do much to mount the electronics and manage the cables because everything was packed in pretty tight and just cushioned by my rat's nest of wiring.  I want to do a better job with my wiring this time around for my antweight (and maybe revisit the wiring for my beetleweight), so I just wanted to hear what some other people had done for mounting the electronics in their bots. 

For holding things in place, did you use zip ties? Mounting tape? Hot glue? Velcro?

For managing wires from ESCs and things, did you leave the wires the length that they were originally and secure them, or did you shorten them?

Questions / Most Useful Tools
« on: February 25, 2016, 07:25:12 am »
For my first two bots I have mostly relied on using hand tools and sending out to have parts cut for me, but I would like to make a wish list of what would be the best set of tools to be able to make my robots all by myself.  I currently have a good rotary tool set, a portable scroll saw, a hand drill, various hand tools (pliers, hex wrenches, etc.), a small plastic vise, soldering tools, a small butane torch set, and a blow torch, and I plan on getting a drill press (I had borrowed my father's before) and maybe one day getting a new 3D printer (sold my old one a little while ago).  I am currently focusing on the insect weight classes (though I have some thoughts about possibly getting into the 12 or 30 lb categories a few years down the road if things go well), and I only have a minuscule amount of experience with machining, so my fabrication experience doesn't extend too far past my first two bots.

My question is what tools would you suggest I consider for a future workshop if I wanted to expand on what I am able to create?  What would be the most useful skills to add to my fabrication repertoire to supplement the soldering, drilling, cutting, and grinding that I already know how to do?

Questions / Armored 3D printed antweights?
« on: November 06, 2015, 05:31:16 pm »
I know that there have been some very successful 3D printed antwieghts, like DDT.

I also know that they can be a be a bit more fragile and snap, like Hercules did at the Franklin Institute recently.

The thought that I had was to make a 3D printed frame for a bot and then cover it with a thin layer of armor.

In this case I've mocked it up as a 3D printed frame with 0.5mm Ti sheets being used to make top and bottom plates as well as armor for the sides and back.  I know that PLA would probably be too brittle for this type of abuse, and I don't have access to a fancy printer that uses nylon and carbon fiber like DDT used.  I could print it out of ABS with my FDM printer, but I think that it might be more shock-resistant if I got some site like Shapeways to print it for me out of something like sintered nylon.  I was thinking that this approach would give it some armor to spread out impacts and protect the plastic frame, but would get a bit of shock absorbtion from the flexibility of the plastic.

Are there any bots out there that have used this type of design successfully?  Would this work pretty well as a type of robot frame design, or is there some glaring flaw that I've overlooked?

Questions / Aluminum Vs Titanium
« on: October 27, 2015, 04:00:22 pm »
I've been shopping around for parts and materials for a potential future antweight bot that I would build entirely by myself, and I've been trying to decide between using aluminum or titanium sheets to make the body.

I've done some rough math, and it looks like I could go with either 0.8mm thick sheets of Grade 5 titanium or 0.05in (1.27mm) thick sheets of 7075-T6 aluminum and achieve roughly the same weight give or take a tenth of an ounce.  Even with the thinner sheets it looks like the titanium would be slightly stronger than the aluminum, but not hugely so.  I also know that titanium is supposed to handle impacts better than aluminum, but my main concern that I have about using it is with the ease of fabrication. 

My rough design involves cutting, drilling, and bending the metal sheets into the desired shape, and largely what I have to do it with is the hand tools and woodworking tools that I have lying around (hammers, vise, dremel, jig saw, drill press, etc), not any type of machine shop type tools that were intended for working with metal.  When I was first thinking about using 7075-T6 aluminum I was just planning to cut it with the right dremel discs or jigsaw blades, find the right drill bits to use in the drill press to make the holes, and cold-bend it with something like a vise and hammer.

While it looks like the titanium might be a small upgrade over the aluminum, my tiny bit of research thus far makes it sound like it might be significantly more difficult to fabricate with.  Where I was planning to cold-bend the aluminum, I have seen recommendations to hot-bend titanium sheets with a large radius so that they don't crack.  Where I was planning to just punch through the aluminum with our drill press, I have read that titanium can get harder during drilling and even blunt steel drill bits.  I don't have much experience fabricating with metal besides a few small holes I have drilled and cuts I have made on some aluminum, and I don't know if these recommendations that I found apply to these types of thin sheets of metal or are just meant for dealing with larger chunks of metal. 

So, here are my questions to anyone who has more metalworking experience than me: Would it be significantly harder to fabricate my bot out of 0.8mm Grade 5 titanium than out of 1.27mm 7075-T6 aluminum, and would the titanium actually give enough of an advantage over the aluminum to justify using it?

Questions / 6061 vs. 7075 Aluminum
« on: October 18, 2015, 08:17:31 pm »
I've got everything ready to go ahead and make an order to get my metal parts cut to make my bot, but before I pull the trigger on this I wanted to get some opinions on what material I should get.  I know that 7075 aluminum is significantly harder than 6061 aluminum, but going by the price of a 12" x 12" x 1/16" sheet of each from McMaster the 7075 aluminum costs about 60% more.  I already have a couple plates of 7075 aluminum to make into the front wedge myself since it will definitely be taking a beating, but the only (outside) parts I'm ordering will be the top, bottom, and back plates.  I'm wondering if I might be safe enough to get away with using 6061 aluminum for these parts since they shouldn't be taking too much abuse if I don't mess up my driving too badly.

What material are you using on your bots for the top/bottom/back?  Would I be relatively safe going with 6061 aluminum, or would it definitely be worth the extra cost of the 7075 aluminum?

Questions / Antweight construction methods
« on: October 03, 2015, 11:07:38 am »
As I'm waiting for the final internal parts for my beetleweight to be delivered, I started to think a little bit about a potential future antweight bot.  After a little bit of glancing around it seems that the most popular construction methods are roughly along the lines of building a hollow box out of aluminum/titanium/UHMW/carbon fiber plates, with a few out there that are made by 3D printing or milling out a block of metal or plastic. 

So I had an idea.  Can you get a more solid chassis like the ones that are machined out of blocks without actually having to use a mill?  The idea is to create a stack of laser cut UHMW layers sandwiched between metal top and bottom layers so that you could make it more solid overall while still creating voids inside for all of the parts, and then all of the layers would be held together by bolts running from the top plate to the bottom plate.  In practice you could improve the fit over what I drew up here by sanding off the corners to get everything closer, but here is my quick-and-dirty mockup:

My initial thoughts are that it could give you a more sturdy frame like with the frames machined from solid blocks, but if it took significant damage you would only have to replace the damaged layers instead of having to machine a whole new frame.

Would this be a decent idea for how to build an antweight?  Or would it be a bad idea because it would not stand up to combat or would quickly put you over the weight limit or something?

Progress Reports / Team Ambient Chaos
« on: September 23, 2015, 11:59:58 am »
Since the first bot I was designing is no longer going to be made and I'm now building a different bot than the one I started the other topic for, I figured that I would start a new topic to chronicle the build progress of what is actually going to be my first bot and any future bots that I wind up making. 

My first bot (Lapsed Pacifist) is going to be a beetleweight "lifting wedge" design inspired by the heavyweight Polar Vortex.  The lifting is going to be powered by two servos with long arms that should be able to lift the nose of the bot about 6" off the ground.  Here is what I have for the design so far; the older design only had a small flat wedge on the front because anything else would have put it overweight, but I went back to the drawing board and reduced the length of the bot by 1" to give me enough weight to play with to make a wider curved wedge:

Once I get all of the holes placed for connecting everything together with nutstrip I am going to 3D print the chassis parts and load all of the electronics into it to take it for a spin, and after making any final tweaks to the design I'm going to get the metal plates cut by waterjet and I'll cut the plastic parts and make the wedge myself.  I can list the parts that I'm using if anyone is interested.

Unfortunately at this rate I'm not sure that I'll have it done in time for the NERC Franklin Institute event next month, but hopefully you'll get to see it in action at events in the Pennsylvania area in the near future.

Progress Reports / First Beetleweight
« on: August 07, 2015, 02:43:37 am »
I am new to the sport and want to dip my toes in by making a fast and tough brick/wedge as my first bot to help me learn some of the intricacies of building, driving, and competing.  At this point I only have a rough idea in my head for the chassis of the bot and a handful of ideas for different types of wedges/scoops, but after several days of researching and shopping I think that I have settled on the internals for the bot.  I figured that having the guts all picked out would make it easier to design the chassis in CAD so everything will fit together, so before I launch into designing and mocking up the chassis I would really appreciate having some more experienced builders look over my components list and give me a sanity check or even some feedback.

I'm including the mixer so that I can just flip a switch on the transmitter to keep the controls the same for driving inverted.  I chose the motors because they seemed to be the best ones I could find that had a good balance of speed and torque, as well as the added benefit of a conveniently available mounting bracket.

I've included a 3S Lipo battery and an ESC that is rated for up to 12V in the list, but I'm on the fence as to whether I should upgrade to a 4S Lipo and an ESC that can take the higher voltage like the Scorpion Wasp.  Would it be worth it for the added speed and pushing power of a 4S, or would I be better off sticking with a 3S to make it easier to LTFD?

Looking forward to having to repair/replace parts during a competition, not counting the (as yet undesigned) structural parts of the bot, what parts would I definitely want to have spares of and what parts would probably have no issues surviving a clash with a decent spinner or drum?

Also, I've been thinking about something like the Spektrum DX5e as a decent transmitter to start me off and hopefully last me through multiple bots, but are there any transmitters that particularly stand out for a high recommendation?

With this and all future updates as I build this bot I fully welcome any suggestions, pointers, and constructive criticism of my designs so that I can make this a learning experience and wind up with the best bot that I can make.

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